Technical Field
This patent application relates to an electromagnetic energy collection device and specifically to rectifiers for energy harvesting or general rectification of ultra-high frequency energy.
Background Information
The integration of photonic devices for low-cost on-chip optical interconnects is of great interest for high speed computing. Additionally, there is a desire in the solar energy industry to tap the potential high theoretical conversion efficiency of rectennas, where highly concentrated coherent light in a waveguide could enable higher rectenna efficiencies.
One of the key elements for both end uses is the efficient integration of a waveguide and a detector. Coupling of light from a planar waveguide to a monolithically integrated detector, such as a tunnel diode or rectenna, can be accomplished in several ways, but it has remained a challenge to do so with high efficiency across a broad spectral band.
There are a variety of applications for tunnel diodes and rectennas, including energy harvesting, rectification, and harmonic mixing for down and up conversion. Dipole, bowtie and spiral have been some of the antenna geometries explored, and the rectifying diodes include p-n junction semiconductor diodes, Schottky metal-semiconductor diodes, and MIM tunnel diodes. The choice of rectifier is dependent on the frequency of electromagnetic energy. The diodes listed above have increasing bandwidth as they rely less upon a capacitive depletion layer for asymmetry of current flow. For conversion of terahertz (THz) frequencies, tunnel diodes made from metal-insulator-metals are the only type of junction to that has the speed to rectify IR and potentially visible light.
Although there has been some success in fabricating dissimilar MIM diodes and obtaining rectification of infrared (IR) energy, the efficiencies reported have been less than 1% due to the limited asymmetry in the current vs. voltage characteristics of the diode.
Some earlier work experimented with creating a Schottky-like diode from a single layer of graphene in contact with a metal electrode, as reported by Nourbakhsh, A, et. al, Applied Physics Letters, 97, 1631010 (2010).
Reference may also be made to rectenna apparatus for solar energy collection, such as in U.S. Pat. No. 8,437,082 entitled “Orthogonal scattering features for solar array” and U.S. Pat. No. 8,735,719 entitled “Leaky solar array with spatially separated collectors”, and U.S. Patent Publication 2014/0182656 entitled “Wideband light energy waveguide and detector”, each assigned to AMI R&D, the assignee of the present application, and each of which are hereby incorporated by reference.